Three-energy-storage frequency modulation control method for triggering flywheel takeover based on target soc interval

Abstract

The application discloses a three-energy-storage frequency modulation control method based on target SOC interval triggering flywheel takeover, and relates to the technical field of power supply systems. The method comprises the following steps: dividing the super capacitor charge state into a target SOC interval and a safety SOC interval; when the super capacitor SOC deviates from the target interval and meets the takeover condition, triggering the flywheel to take over the primary frequency modulation power, so that the super capacitor exits the high-load regulation state and enters the standby state; and when the allowed energy exchange condition is met, performing super capacitor working point regression control to restore its frequency modulation capability. When the system frequency deviation continuously reaches the long-time support threshold, the compressed air takes over the secondary frequency modulation power. Through the target interval triggering and conditional regression mechanism, the application solves the problems of SOC out-of-control of the fast energy storage and interruption of frequency modulation in the prior art, clearly defines the connection boundary of the primary and secondary frequency modulation, and improves the continuity, stability and engineering implementability of the three-energy-storage collaborative frequency modulation.

Description

Technical Field

[0001] This invention relates to the field of power supply system technology, and specifically to a three-energy storage frequency regulation control method based on flywheel take-off triggered by a target SOC range. Background Technology

[0002] With the continuous increase in the proportion of renewable energy connected to the grid, the net load fluctuation of the power supply system has intensified, and the frequency deviation and frequency change rate exhibit characteristics of strong randomness, frequent disturbances, and a coexistence of short-term sharp changes and continuous offsets. To improve the frequency support capability of the power supply system under the high proportion of renewable energy access, existing technologies typically adopt three types of solutions: single energy storage frequency regulation, hybrid energy storage with separate functions for frequency regulation, and coordinated deployment of three types of energy storage. Single energy storage frequency regulation often uses batteries, flywheels, or supercapacitors to participate in primary frequency regulation alone. This mode has a simple architecture and is easy to deploy. However, in this mode, the same energy storage unit needs to simultaneously take into account both rapid transient response and short-term continuous power support. Hybrid energy storage with separate functions for frequency regulation commonly includes combinations such as supercapacitor + battery, flywheel + battery, and supercapacitor + compressed air. This mode achieves fast and slow division of labor based on the inherent characteristics of energy storage power type and energy storage energy type. Power-type fast energy storage such as flywheels and supercapacitors undertake primary frequency regulation and high-frequency power fluctuation smoothing; energy-type slow energy storage such as batteries and compressed air is responsible for low-frequency continuous power support. While existing control methods can balance response speed and energy support to some extent, they mostly employ fixed output ratios and fixed operating priorities, lacking dynamic adaptive adjustment capabilities. The coordinated sequential deployment of multiple energy storage systems primarily targets scenarios involving the combined application of various energy storage types, such as flywheels, supercapacitors, and compressed air. In this mode, different types of energy storage devices are coordinated and scheduled according to their characteristics and operating stages to improve the frequency regulation capability of the power supply system at different time scales. For example, supercapacitors and flywheels jointly undertake the initial instantaneous high-frequency regulation response, while compressed air provides subsequent long-term steady-state support. Although this mode aligns with the multi-time-scale frequency regulation requirements, existing research does not adequately consider the maintenance of the steady-state operating point between flywheels and supercapacitors, the mutual takeover mechanism under disturbance conditions, and the smooth switching mechanism; furthermore, there is a lack of unified quantitative criteria for determining the switching of operating conditions and power transfer between primary and secondary frequency regulation.

[0003] In summary, existing frequency regulation control methods have gradually evolved from single-energy storage frequency regulation to a hybrid energy storage system with division of labor and coordinated deployment of three energy storage systems. However, it is still difficult to achieve an effective balance among rapid instantaneous frequency regulation response, stable maintenance of the operating points of each energy storage system's SOC, and long-term power support across time scales. There is still considerable room for optimization in terms of adaptability and operational economy. Summary of the Invention

[0004] This invention provides a three-energy storage frequency regulation control method based on flywheel take-off triggered by target SOC range. The purpose is to solve the technical problem of achieving effective coordinated balance among fast instantaneous frequency regulation response, stable maintenance of the operating point of each energy storage SOC, and long-term power support across time scales in the prior art.

[0005] In view of the above problems, the present invention provides a three-energy storage frequency regulation control method and system based on flywheel take-off triggered by target SOC range.

[0006] In a first aspect, the present invention provides a three-energy storage frequency regulation control method based on flywheel take-off triggered by a target SOC range, comprising: Real-time acquisition of system operating status parameters, including the measured system frequency and the state of charge of the supercapacitor; The state of charge of the supercapacitor is divided into a target SOC range and a safe SOC range. The target SOC range is used to characterize the preferred operating range in which the supercapacitor maintains its continuous and fast frequency modulation capability, and the safe SOC range is used to characterize the safe operating boundary of the supercapacitor. The target SOC range is located within the safe SOC range. The absolute value of the difference between the system's rated frequency and the system's measured frequency is calculated as the system frequency deviation; When the supercapacitor's state of charge is within the target SOC range and the system frequency deviation is greater than or equal to the primary frequency modulation start threshold, the supercapacitor will bear the primary frequency modulation power. When the state of charge of the supercapacitor deviates from the target SOC range and meets the preset takeover conditions, the flywheel is triggered to take over the primary frequency regulation power, causing the supercapacitor to exit the high load regulation state and enter the recovery state. When the conditions for permissible energy exchange are met, supercapacitor operating point regression control is executed to restore the supercapacitor's state of charge to the target SOC range. Once the supercapacitor's state of charge returns to the target SOC range and remains there for a preset dwell time, the flywheel gradually exits at a preset slope, and the system returns to the operating state where the supercapacitor performs primary frequency regulation. When the system frequency deviation is greater than or equal to the secondary frequency regulation start threshold and the duration of this state reaches the long-term support threshold, the secondary frequency regulation power is undertaken by compressed air energy storage, forming a hierarchical collaborative control of rapid energy storage and energy-type energy storage. The secondary frequency regulation start threshold is greater than the primary frequency regulation start threshold.

[0007] The technical solution provided in this invention has at least the following technical effects or advantages: (1) Improve the continuity of primary frequency regulation and the sustainable availability of fast energy storage: This invention uses the target SOC range rather than the safe SOC range as the basis for switching the regulation state of the supercapacitor, and triggers the flywheel to take over the primary frequency regulation before it deviates from the optimal operating range. This invention can reduce the problems of power limiting, frequent shutdown and reduced available frequency regulation margin caused by the continuous drift of the supercapacitor SOC, thereby improving the continuity of primary frequency regulation and the operational stability of the fast energy storage layer.

[0008] (2) Ensuring Engineering Self-Consistency and Achieving Conditional Operating Point Regression: This invention adopts a control chain of "flywheel first taking over frequency regulation, supercapacitor first exiting high-load state, and then performing operating point regression under permitted energy replenishment conditions." This solves the problem of untimely SOC recovery or unreasonable recovery process in existing technologies. By clarifying the takeover process before recovery and the recovery implementation conditions, this invention ensures the coordination between the SOC regression process and the system energy exchange conditions, enhances the engineering self-consistency of the scheme, and improves the sustainable availability of the supercapacitor in subsequent frequency regulation processes.

[0009] (3) Clarifying the boundary between primary and secondary frequency regulation and improving engineering feasibility: This invention avoids the problem of blindly intervening in slow energy storage according to a fixed time sequence in existing schemes by comprehensively judging whether the rapid main response is completed, whether the continuous support demand has exceeded the time limit, and the pressure feasible domain of compressed air energy storage. This scheme makes the timing of secondary frequency regulation more in line with actual needs, while improving the clarity of the control strategy hierarchy and the feasibility of engineering implementation. Attached Figure Description

[0010] Figure 1 A flowchart illustrating the three-energy storage frequency modulation control method based on target SOC range-triggered flywheel take-off provided in an embodiment of the present invention; Figure 2 This is a regression diagram of the supercapacitor's state of charge, flywheel connection, and operating point in this invention. Figure 3 This is a diagram showing the smooth connection between the supercapacitor and flywheel during the primary frequency modulation stage of this invention. Figure 4 This is a diagram illustrating the secondary frequency modulation boundary determination and compressed air intervention of the present invention. Figure 5 This is a schematic diagram of the structure of the three-energy storage frequency modulation control unit based on the target SOC range triggering flywheel take-off provided in an embodiment of the present invention. Detailed Implementation

[0011] This invention provides a three-energy storage frequency regulation control method and system based on target SOC range-triggered flywheel take-off, which is used to address the technical problem of low cross-departmental resource utilization in the prior art.

[0012] Example 1, as Figure 1As shown, this invention provides a three-energy storage frequency regulation control method based on flywheel take-off triggered by a target SOC range, the method comprising: S1: Real-time acquisition of system operating status quantities, including the measured system frequency and the state of charge of the supercapacitor.

[0013] Specifically, frequency sensors (such as phase measurement units or high-precision frequency transmitters) deployed at key nodes of the power supply system acquire the system's measured frequency in real time with millisecond-level sampling periods. The control unit compares the measured frequency acquired in each sampling period with the system's rated frequency, calculating the real-time frequency deviation. This deviation value is used to determine whether the primary frequency regulation start-up threshold is met. Simultaneously, voltage and current sensors integrated within the supercapacitor energy storage unit monitor its terminal voltage and branch current in real time. Using the ampere-hour integral method or a state estimation algorithm combined with an equivalent circuit model, the supercapacitor's state of charge (SOC) is calculated or estimated in real time. The SOC value accurately characterizes the real-time energy reserve level of this rapid energy storage. The control unit continuously compares this measured SOC value with a preset target SOC range. When the SOC is within this range, it indicates that the supercapacitor is in an ideal operating range that provides optimal power response and cycle life; once the SOC deviates from this range, it indicates a decrease in its frequency regulation margin or an increase in the risk of overcharging / over-discharging. Therefore, real-time data from the SOC is an absolute prerequisite for implementing the core innovation of this patent, namely, triggering flywheel take-off in advance when deviating from the target range, rather than waiting to reach the safety boundary and then passively protecting it.

[0014] In summary, the synchronous, high-speed, and accurate acquisition of both the system's measured frequency and the supercapacitor's State of Charge (SOC) forms the perception foundation for the aforementioned collaborative control strategy. Frequency data drives the decision on whether frequency regulation is needed, while SOC data determines which entity should perform frequency regulation with what priority. The real-time interaction and joint judgment of these two data points enable the control system to move beyond simply responding to frequency deviations, thereby fundamentally solving the problem of frequency regulation continuity interruptions caused by poor SOC management in rapid energy storage technologies. For example, in the scenario of new energy power plants, facing frequency fluctuations caused by sudden changes in wind speed, it is precisely by quickly capturing sudden frequency drops and making real-time judgments that the supercapacitor's SOC has dropped to 0.43 that the system can immediately trigger flywheel takeover. This allows for a seamless switchover of the main power support before the frequency deteriorates significantly and the supercapacitor reaches its safety limit, ensuring continuous high-quality output of frequency regulation services.

[0015] S2: Divide the state of charge of the supercapacitor into a target SOC range and a safe SOC range. The target SOC range is used to characterize the preferred operating range for the supercapacitor to maintain continuous and fast frequency modulation capability. The safe SOC range is used to characterize the safe operating boundary of the supercapacitor. The target SOC range is located within the safe SOC range.

[0016] Specifically, dividing the supercapacitor's state of charge (SOC) into a target SOC range and a safe SOC range is the core of its forward-looking and collaborative control architecture. The safe SOC range is an absolute safe operating boundary determined based on the supercapacitor's chemical characteristics and lifespan testing; its function is to prevent equipment damage and it serves as a passive protection layer. The target SOC range, strictly within the safe range, is an actively optimized operating area set based on the supercapacitor's characteristics of optimal charge / discharge efficiency, fastest power response, and best cycle life at the mid-range of rated voltage. Its function is to maintain the supercapacitor's optimal operating state and sustainable frequency regulation capability. During operation, the control unit continuously compares the supercapacitor's SOC with these two ranges: when the supercapacitor's SOC is within the target range, the supercapacitor prioritizes primary frequency regulation; once the SOC deviates from the target range but remains within the safe range, the system immediately triggers the flywheel to take over early, causing the supercapacitor to exit high load to prevent its condition from deteriorating. This refined hierarchical management upgrades the state of charge (SOC) of the tiered capacitor from a traditional binary judgment of safety to continuous management of optimality, early warning, and protection. This proactively maintains the health of energy storage while the frequency regulation task is still in progress, directly solving the problems of disconnect between SOC recovery and frequency regulation processes in existing technologies, as well as the easy over-limiting of power in fast energy storage. By coordinating in advance during frequency disturbances rather than protecting afterward, it ensures the continuity of primary frequency regulation and creates conditions for subsequent conditional operating point return, ultimately improving the overall availability and frequency regulation economy of the fast energy storage layer.

[0017] S3: Calculate the absolute value of the difference between the system's rated frequency and the system's measured frequency as the system frequency deviation.

[0018] Specifically, in the three-energy storage frequency regulation control system, a high-precision frequency sensor collects the actual operating frequency of the power supply system in real time at millisecond intervals, i.e., the measured frequency of the system. This frequency will deviate from its design standard value—the rated frequency of the system (usually 50Hz or 60Hz)—due to factors such as sudden load changes, fluctuations in new energy power, or faults. The control unit subtracts the measured frequency acquired in each sampling cycle from the rated frequency and calculates the absolute value of the difference to obtain the real-time system frequency deviation. The absolute value of this frequency deviation is the core indicator for quantifying the degree of instantaneous power imbalance in the power supply system. Its magnitude and trend directly and continuously drive the entire hierarchical control strategy: it is not only used to determine whether the primary frequency regulation start-up threshold has been reached to decide whether to mobilize the supercapacitor for rapid power support; its continuous amplitude and direction are also used to assess whether the allowable energy exchange conditions after flywheel takeover are met, thereby safely initiating the supercapacitor's operating point return; at the same time, the duration and level of this deviation are key bases for determining whether secondary frequency regulation or slow energy storage intervention such as compressed air energy storage should be initiated. Therefore, the system frequency deviation is not an isolated monitoring parameter, but a core link connecting the physical power supply system status and the algorithm control logic. It integrates discrete status judgments, power allocation and switching commands into a dynamic response and collaborative optimization closed loop, ensuring a precise balance between the speed of primary frequency regulation, the stability of the energy storage operating point and the continuity of secondary frequency regulation.

[0019] S4: When the supercapacitor's state of charge is within the target SOC range and the system frequency deviation is greater than or equal to the primary frequency modulation start threshold, the supercapacitor will bear the primary frequency modulation power.

[0020] Specifically, the system determines whether to trigger frequency regulation by real-time monitoring of the supercapacitor's State of Charge (SOC) and the system frequency deviation. When the SOC value is within the target SOC range, it indicates that the supercapacitor's charging and discharging state is suitable for frequency regulation and can maintain continuous and rapid frequency regulation capabilities. When the system frequency deviation is greater than or equal to the primary frequency regulation initiation threshold, it indicates significant frequency fluctuations in the power grid, requiring the initiation of frequency regulation. By inputting these two parameters into the control unit, the control unit automatically determines whether the conditions for initiating primary frequency regulation are met. When the supercapacitor's SOC is within the target range and the system frequency deviation reaches the trigger condition, the control unit instructs the supercapacitor to begin undertaking frequency regulation power, rapidly responding to changes in the power grid frequency and maintaining system stability. This technical feature ensures that the supercapacitor can participate in frequency regulation under optimal operating conditions, thereby avoiding problems such as insufficient energy storage capacity or limited power output due to excessively low SOC. Through this collaborative work, the system can improve the accuracy and continuity of frequency regulation response, solving the problem of low frequency regulation efficiency caused by unstable or frequent switching of energy storage unit states in existing technologies, and improving the stability and reliability of the power grid.

[0021] S5: When the state of charge of the supercapacitor deviates from the target SOC range and meets the preset takeover conditions, the flywheel is triggered to take over the primary frequency regulation power, causing the supercapacitor to exit the high load regulation state and enter the waiting recovery state.

[0022] Specifically, when the state of charge (SOC) of the supercapacitor deviates from the target range and the duration reaches a preset first time threshold, the system determines that the fast energy storage layer needs to switch states. At this time, the control unit generates a flywheel takeover command. This command calculates the flywheel reference power based on real-time collected frequency deviation and frequency change rate. The flywheel then outputs primary frequency regulation power to take over the regulation tasks originally performed by the supercapacitor. Simultaneously, the control unit issues a derating command to the supercapacitor, causing it to exit the high-load regulation state and enter a recovery state, thereby preventing further deterioration of the supercapacitor's SOC. Figure 2 As shown, during a frequency regulation phase, the initial State of Charge (SOC) of the supercapacitor (SCES) is within the target range. As a system frequency deviation occurs, the SCES responds rapidly to meet the frequency regulation requirements, causing the SCES SOC to drop rapidly. When the SCES SOC falls below the lower limit of the target range, the control unit detects this deviation and immediately issues a flywheel takeover signal. Upon receiving the command, the flywheel (FES) quickly takes over the main frequency regulation power, while the SCES enters a standby state. During this period, the system monitors the power supply system's operating condition in real time. When the permissible energy exchange conditions are met, the control unit issues a return-to-operation-point signal, activating the supercapacitor return control loop. Subsequently, under the power regulation, the SCES SOC begins to approach the target range until it successfully returns to the target range and, after a preset dwell time, the system completes a smooth state switching cycle. Figure 3 As shown, during the smooth takeover process in the first frequency modulation phase, the system frequency modulation demand (blue curve) exhibits a step change. In the initial response phase (0-10s), the supercapacitor (SCES, red curve) takes the lead in undertaking the main regulation task due to its rapid charging and discharging characteristics, while the flywheel (FESS, yellow curve) remains on standby at low power, ensuring instantaneous capture of high-frequency components. As the SCES continues to discharge, its state of charge approaches the lower limit (triggering...). Figure 2 (The takeover logic in the process) ensures a smooth transfer of system control: the SCES power (red curve) gradually returns to zero and exits high-load regulation, while the flywheel power (yellow curve) rapidly increases and takes over the full frequency regulation task. The two achieve perfect power complementarity and seamless transition during the dynamic process, ensuring that the total supporting power (purple dashed line) accurately and continuously tracks the frequency regulation command, effectively solving the frequency regulation interruption problem caused by the limited state of a single energy storage unit in existing technologies.

[0023] In another embodiment, the flywheel takes over the primary frequency regulation power using any of the following methods: full takeover, proportional takeover, or gradual load increase. During flywheel takeover, the supercapacitor's output power is adjusted proportionally according to a power retention factor, which represents the ratio of the supercapacitor's actual output power to the primary frequency regulation power. The power retention factor ranges from 0 to 1 depending on the degree of flywheel takeover. When the flywheel takes over completely, the power retention factor equals 0, the supercapacitor's actual output power drops to 0, and the supercapacitor ceases to bear the primary frequency regulation power. When the flywheel takes over proportionally, the power retention factor is a fixed value greater than 0 and less than 1, or a time-varying value; when the flywheel takes over gradually, the power retention factor gradually decreases over time to a target value.

[0024] S6: When the allowable energy exchange conditions are met, execute supercapacitor operating point regression control to restore the supercapacitor's state of charge to the target SOC range.

[0025] Specifically, when the supercapacitor is in a state awaiting recovery, the power supply system monitors the frequency deviation, frequency deviation trend, and bus power balance margin in real time to determine whether the permissible energy exchange conditions are met. Permissible energy exchange conditions include: the system frequency deviation is less than or equal to a preset frequency recovery threshold, which is less than the secondary frequency regulation start threshold; the signs of the frequency deviations in adjacent control cycles are opposite; the real-time acquired system load level is within a preset low load range; the power of each energy storage unit and the bus voltage of the common DC bus are collected in real time, and the DC bus power balance margin is calculated and meets the preset margin threshold; after the system enters the long-term support phase of secondary frequency regulation, the compressed air energy storage undertakes the secondary frequency regulation power. For example, if the sign of the frequency deviation in adjacent control cycles is reversed, it indicates that the system is temporarily in a power adjustable window, thus determining that the permissible energy exchange conditions are met. The control unit then activates the supercapacitor return control loop, generating a return power command based on the difference between the target SOC range center value and the current SOC. This command, after being limited, drives the supercapacitor to perform charging or discharging operations, causing its state of charge to return to the target range along a gentle slope. For example, in the frequency regulation scenario of new energy power plants, if the power supply system frequency stabilizes and there is surplus power on the DC bus during flywheel takeover, the system will initiate supercapacitor recharge, raising its SOC from the deviation of 0.4 to 0.5, thus avoiding secondary disturbances caused by forced recovery. This control logic closely integrates algorithm-level condition judgment with physical-level power regulation, solving the problems of unclear energy sources and control instability caused by the disconnect between recovery timing and system operating conditions in existing technologies. It ensures that the supercapacitor neither impacts the power grid nor fails to effectively restore frequency regulation capability during the recovery process.

[0026] S7: When the supercapacitor's state of charge returns to the target SOC range and remains there for a preset dwell time, the flywheel gradually exits at a preset slope, and the system returns to the operating state where the supercapacitor undertakes primary frequency regulation.

[0027] Specifically, the power supply system monitors the supercapacitor's state of charge (SOC) in real time. Once the SOC returns to the target range and remains there for a preset time, the control unit generates a flywheel exit command. The flywheel output power is decreased periodically according to a preset slope, while the supercapacitor output power is increased at the same slope, achieving a smooth transfer of frequency regulation responsibilities. This process tightly couples the algorithm-level slope rate limitation with the physical-level power device actions, ensuring that the power difference remains within the system's tolerance range. For example, in a renewable energy power station, when the supercapacitor's SOC stabilizes around 0.5 and remains there for 5 seconds, the flywheel power decreases linearly at a rate of 10% of the rated power per second, and the supercapacitor synchronously and linearly assumes the primary frequency regulation task. This method solves the problem of "fixed rapid energy storage layer switching threshold and lack of dynamic adaptive adjustment" in the background technology, avoiding the power gap caused by the sudden withdrawal of the flywheel or the impact caused by the hasty entry of the supercapacitor in the existing technology. This achieves the technical effect of "improving the continuity of primary frequency regulation and the sustainable availability of rapid energy storage," ensuring the operational stability of the three-energy storage system under complex operating conditions.

[0028] S8: When the system frequency deviation is greater than or equal to the secondary frequency regulation start threshold and the duration of this state reaches the long-term support threshold, the secondary frequency regulation power is undertaken by compressed air energy storage, forming a hierarchical collaborative control of rapid energy storage and energy-type energy storage. The secondary frequency regulation start threshold is greater than the primary frequency regulation start threshold.

[0029] Specifically, the power supply system collects frequency deviation data in real time and compares it with a preset secondary frequency regulation start threshold. When the absolute value of the detected frequency deviation is greater than or equal to the secondary frequency regulation start threshold and the duration reaches the long-term support threshold, the system is determined to enter the secondary frequency regulation stage. The control unit then collects the pressure of the gas storage tank in real time through a pressure sensor and calculates the pressure change rate. Only when the pressure of the gas storage tank is between the minimum and maximum allowable pressures and the pressure change rate does not exceed the preset upper limit will a start command be sent to the compressed air energy storage, while simultaneously coordinating the flywheel and supercapacitor to adjust the output power. The compressed air energy storage can also be replaced by pumped hydro storage, hydrogen storage, long-duration batteries, or other energy storage types. These types of energy storage all have long-term power support capabilities and only need to meet pressure or capacity feasibility domain verification to be connected to the control link. Figure 4As shown, during the secondary frequency regulation boundary determination and compressed air (CAES) intervention process, the system monitors the continuous frequency deviation time (tsup, blue solid line) in real time. As the system frequency deviation continues, the blue curve linearly increases to the preset secondary frequency regulation initiation threshold (T3, dashed line). Simultaneously, the control unit performs pressure feasibility domain verification for compressed air energy storage (pressure density index shown by the red dashed line). Only when both the duration condition and pressure state condition are met will the system issue a compressed air intervention flag (orange solid line), allowing compressed air to undertake the long-term secondary frequency regulation task. This mechanism effectively avoids blind intervention or insufficient support caused by slow energy storage being infeasible due to state limitations.

[0030] This mechanism, through dual threshold judgments at the algorithmic level, ensures that compressed air only intervenes in long-term secondary frequency regulation tasks when the conditions are feasible and the demand is clear, effectively avoiding resource waste caused by insufficient pressure or premature intervention of slow energy storage. For example, in the application of new energy power stations, if the system frequency deviation continuously reaches the 30-second threshold and the air storage tank pressure is within the safe and feasible range of 15MPa to 20MPa, the control unit will determine that the long-term support demand is established, and then trigger the orange flag, with compressed air energy storage taking over the main frequency regulation power. At the same time, the flywheel gradually withdraws according to the preset slope, and the supercapacitor enters standby mode. This strategy clarifies the connection boundary between primary and secondary frequency regulation, significantly improving the collaborative stability and engineering feasibility of the three-energy storage system across multiple time scales.

[0031] Example 2, as Figure 5 As shown, this invention provides a three-energy storage frequency regulation control system based on flywheel take-off triggered by a target SOC range. The system includes: Data acquisition unit: configured to acquire system operating status quantities in real time, including the measured system frequency, supercapacitor state of charge, and compressed air energy storage pressure; Supercapacitor energy storage unit: configured to output primary frequency regulation power when the state of charge is within the target SOC range and the system frequency deviation meets the primary frequency regulation start-up conditions; after receiving the flywheel take-over command, exit the high load regulation state and enter the waiting recovery state; when the allowable energy exchange conditions are met, execute operating point regression control to restore the state of charge to the target SOC range.

[0032] Flywheel energy storage unit: configured to undertake primary frequency regulation main power output when receiving takeover command; after the supercapacitor's state of charge recovers to the target SOC range and maintains a preset dwell time, it gradually exits the frequency regulation state according to a preset slope.

[0033] Compressed air energy storage unit: configured to undertake secondary frequency regulation power after the system frequency deviation is greater than or equal to the secondary frequency regulation start threshold and the duration of this state reaches the long-term support threshold, and after passing the pressure feasibility domain verification; wherein, compressed air energy storage can be replaced by pumped hydro storage, hydrogen energy storage, long-term battery or other energy storage with long-term support capability.

[0034] Control unit: Divides the target SOC range and the safe SOC range; when the supercapacitor's state of charge deviates from the target SOC range and meets the preset takeover conditions, generates a flywheel takeover command; determines whether the conditions for permissible energy exchange are met, and activates the supercapacitor return control loop when they are met; comprehensively determines the secondary frequency modulation start-up conditions and the pressure feasible range, and generates a compressed air energy storage start-up command; and coordinates the power distribution and smooth switching between each energy storage unit.

[0035] This invention solves the problems of continuous SOC drift and frequency regulation interruption in existing technologies for fast energy storage by using the target SOC range rather than the safety boundary as the basis for state switching, combined with flywheel takeover and conditional operating point regression mechanisms. This improves the continuity of primary frequency regulation and the sustainable availability of fast energy storage. At the same time, through hierarchical collaborative control based on long-term support demand and pressure feasible domain, the connection boundary between primary and secondary frequency regulation is clarified, avoiding the blind intervention of slow energy storage. Thus, while ensuring the frequency stability of the power supply system, it significantly enhances the engineering self-consistency and operational economy of three-energy storage collaborative frequency regulation.

[0036] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A three-energy storage frequency regulation control method based on flywheel take-off triggered by target SOC range, characterized in that, include: Real-time acquisition of system operating status parameters, including the measured system frequency and the state of charge of the supercapacitor; The state of charge of the supercapacitor is divided into a target SOC range and a safe SOC range. The target SOC range is used to characterize the preferred operating range in which the supercapacitor maintains its continuous and fast frequency modulation capability, and the safe SOC range is used to characterize the safe operating boundary of the supercapacitor. The target SOC range is located within the safe SOC range. The absolute value of the difference between the system's rated frequency and the system's measured frequency is calculated as the system frequency deviation; When the supercapacitor's state of charge is within the target SOC range and the system frequency deviation is greater than or equal to the primary frequency modulation start threshold, the supercapacitor will bear the primary frequency modulation power. When the state of charge of the supercapacitor deviates from the target SOC range and meets the preset takeover conditions, the flywheel is triggered to take over the primary frequency regulation power, causing the supercapacitor to exit the high load regulation state and enter the recovery state. When the conditions for permissible energy exchange are met, supercapacitor operating point regression control is executed to restore the supercapacitor's state of charge to the target SOC range. Once the supercapacitor's state of charge returns to the target SOC range and remains there for a preset dwell time, the flywheel gradually exits at a preset slope, and the system returns to the operating state where the supercapacitor performs primary frequency regulation. When the system frequency deviation is greater than or equal to the secondary frequency regulation start threshold and the duration of this state reaches the long-term support threshold, the secondary frequency regulation power is undertaken by compressed air energy storage, forming a hierarchical collaborative control of rapid energy storage and energy-type energy storage. The secondary frequency regulation start threshold is greater than the primary frequency regulation start threshold.

2. The three-energy storage frequency regulation control method based on target SOC range-triggered flywheel take-off as described in claim 1, characterized in that, The preset takeover condition is specifically: the duration for which the supercapacitor's state of charge continuously deviates from the target SOC range reaches a first time threshold.

3. The three-energy storage frequency regulation control method based on target SOC range-triggered flywheel take-off as described in claim 1, characterized in that, The flywheel take-off primary frequency regulation power can be achieved through any one of the following methods: full take-off, proportional take-off, or gradual increase in power.

4. The three-energy storage frequency regulation control method based on target SOC range-triggered flywheel take-off as described in claim 3, characterized in that, During flywheel takeover, the output power of the supercapacitor is adjusted proportionally according to the power retention factor, which represents the ratio of the actual output power of the supercapacitor to the primary frequency modulation power. The power retention factor takes a value between 0 and 1 depending on the degree of flywheel takeover.

5. The three-energy storage frequency regulation control method based on target SOC range-triggered flywheel take-off as described in claim 4, characterized in that, When the flywheel takes full control, the power retention factor is equal to 0, the actual output power of the supercapacitor drops to 0, and the supercapacitor withdraws from primary frequency regulation power handling.

6. The three-energy storage frequency regulation control method based on target SOC range-triggered flywheel take-off as described in claim 4, characterized in that, When the flywheel adopts a proportional load-bearing method, the power retention coefficient is a fixed value or a time-varying value that is greater than 0 and less than 1; when the flywheel adopts a progressive load-bearing method, the power retention coefficient gradually decreases to the target value over time.

7. The three-energy storage frequency regulation control method based on target SOC range-triggered flywheel take-off as described in claim 1, characterized in that, The permitted energy exchange conditions include at least one of the following: the system frequency deviation is less than or equal to a preset frequency recovery threshold, and the frequency recovery threshold is less than the secondary frequency modulation start threshold; the positive and negative signs of the frequency deviations of adjacent control cycles are opposite. The real-time system load level is within the preset low load range; the power of each energy storage unit and the bus voltage of the common DC bus are collected in real time, and the DC bus power balance margin is calculated and meets the preset margin threshold; after the system enters the long-term support stage of secondary frequency regulation, the secondary frequency regulation power is undertaken by compressed air energy storage.

8. The three-energy storage frequency regulation control method based on target SOC range-triggered flywheel take-off as described in claim 1, characterized in that, The operating point regression control specifically involves determining the charging or discharging power of the supercapacitor based on the deviation between the target state of charge and the actual state of charge, wherein the charging or discharging power does not exceed the rated power of the supercapacitor, and the target state of charge is the state of charge corresponding to the target SOC range.

9. The three-energy storage frequency regulation control method based on target SOC range-triggered flywheel take-off as described in claim 1, characterized in that, Before the compressed air energy storage is used to undertake the secondary frequency regulation power, the method further includes: collecting the pressure of the compressed air energy storage tank in real time through a pressure sensor and calculating the pressure change rate; ensuring that the pressure of the storage tank is between the minimum allowable pressure and the maximum allowable pressure, and that the pressure change rate does not exceed the upper limit of the pressure change rate.

10. The three-energy storage frequency regulation control method based on target SOC range-triggered flywheel take-off as described in claim 1, characterized in that, The compressed air energy storage can also be pumped hydro storage, hydrogen energy storage, long-duration batteries, or other energy storage types.

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